1. Field of the Invention
The present invention relates to a micro-step driving method of a stepping motor that controls a rotation angle by counting pulses of current, and relates to an electrically driven device in which a moving member is moved in accordance with a prescribed path by a stepping motor driven by micro-stepping.
2. Description of the Related Art
Conventionally, a stepping motor has been widely used as a drive source of various electrically driven devices. A micro-step driving technique is known for smoothly rotating such stepping motors. When the stepping motor of the electrically driven device is controlled by being rotated or stopped, the stepping motor structurally has a position to stably stop at. For example, in the case of a stepping motor using two-phase drive, a two-phase position of a rotor is a stable stop point. In the micro-step drive, when the motor is controlled by having the stable stop point as a start point, the electrically driven device can be accurately controlled.
As described above, in the micro-step drive of the stepping motor, the electrically driven device can be accurately controlled by controlling the motor by having the stable stop point as the start point. However, when the motor is controlled by having an intermediate step position, which is not the stable stop position defined by the start point, the motor is stopped at the unstable intermediate step position, and displacement occurs in a rotation angle of the rotor. Moreover, problems occur because as the positional differences and displacement accumulate, accuracy will be lost. Such problems may occur, for example, when the motor is controlled by having as the start point, a count value at the time when a carriage is positioned at a home position by a flatbed scanner.